Hardness Ratings (HRC) in Tool and Die Steel

 

Virat Steels | India's Leading Tool and Die Steel Supplier

If you've ever looked at a tool steel datasheet and wondered what "58 HRC" means and why it matters for your die or mould. Hardness is one of the most critical properties in tool and die steel selection. Get it right, and your tooling performs reliably for thousands of production cycles. Get it wrong, and you're facing premature wear, unexpected cracking, or both. This complete blog explains what is the Rockwell C scale means, maps HRC ranges to every major tool steel grade, and shows you exactly how to choose the right hardness for your application.

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 What is Hardness in Steel and Why Does It Matter?

 In simple terms, hardness is a material’s ability to resist dents, scratches, or permanent deformation under pressure.

For tool and die steel, hardness is one of the most important properties because it affects:

·         Wear resistance – resists abrasion and surface wear

·         Edge retention – keeps cutting tools sharper for longer

·         Compressive strength – withstands heavy forming pressure

·         Dimensional stability – maintains shape and accuracy during production

However, hardness always comes with a trade-off: toughness.
As hardness increases, the steel can become more brittle and prone to cracking under impact.

So, the right steel grade and hardness level should provide the best balance of wear resistance and toughness for the application.

 What is the Rockwell Hardness Test?

 The Rockwell hardness test is the most widely used hardness measurement method in the tool steel industry.

 The Rockwell hardness test checks how hard a material is by measuring how deep a diamond cone goes into its surface.

It works in 3 simple steps:

1.     Minor load applied – A small force (10 kgf) is applied first to set the starting point and remove surface unevenness.

2.     Major load applied – A bigger force (150 kgf for HRC) pushes the diamond into the material.

3.     Load removed – The big force is removed, and the machine measures how deep the mark remains.

Result:

·         Less depth = harder material = higher HRC

·         More depth = softer material = lower HRC

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 Understanding HRC -The Rockwell C Scale

 HRC stands for Hardness Rockwell C -meaning the result was obtained using the Rockwell C scale. It is the standard unit used to express the hardness of virtually all tool and die steels.

 The HRC scale for tool steels runs approximately from 20 HRC(soft, annealed or pre-hardened low-alloy steel) to 68 HRC (the upper limit of conventional hardened tool steel). Here is how the HRC range maps to practical tool steel conditions:

HRC Range	Condition / Category	In Practice
20-35HRC	Soft / pre-hardened	Easily machined; P20 mould steel supply condition
36-44 HRC	Medium Hardness	Good toughness; forging dies for heavy impact
45-52 HRC	Hard	Balanced wear resistance and toughness; H13 die casting dies
53-60 HRC	Very Hard	High wear resistance; D2 cold work dies, punches
61-66 HRC	Extremely Hard	Maximum wear resistance; M2, M42 high-speed steel cutting tools
Above 66 HRC	Ultra Hard	Extremely brittle; not typical for standard die steels

 HRC vs HRB vs HRA — Which Scale Applies to Tool Steel?

HRC	HRB	HRA
Indenter: Diamond cone	Indenter: 1/16" steel ball	Indenter: Diamond cone
Major load: 150 kgf	Major load: 100 kgf	Major load: 60 kgf
Range: Approx 20–70 HRC	Range: Approx 0–100 HRB	Range: for very hard materials
Used For: All hardened and heat-treated tool steels, die steels, high-speed steels, and hardened alloy steels	Used For: Softer steels (mild steel, annealed low-alloy steel), copper alloys, aluminium alloys	Used For: Cemented carbides, case-hardened surfaces, thin hardened layers

You cannot directly compare numbers from different Rockwell scales. 60 HRC and 60 HRB are not equivalent, they refer to completely different hardness levels. Always confirm which scale a hardness value is expressed in before comparing materials.

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 HRC vs Brinell (HB) vs Vickers (HV): Approximate conversion table for tool steel

While HRC is the standard for tool steel, you will also encounter Brinell (HB or HBW) and Vickers (HV) hardness values — particularly on material certificates from European suppliers who use DIN specifications.

HRC	HB (Brinell)	HV (Vickers)	Approx. Tensile Strength
20	226	238	~780 MPa
25	253	266	~870 MPa
30	286	302	~995 MPa
35	327	345	~1140 MPa
40	371	392	~1310 MPa
45	421	446	~1500 MPa
48	455	481	~1630 MPa
50	481	509	~1720 MPa
52	512	544	~1820 MPa
55	560	595	~1980 MPa
58	615	655	~2160 MPa
60	654	697	~2280 MPa
62	746	746	~2400 MPa

 *Note: These are approximate conversions. For precise engineering calculations, always use the original test method. Conversion between hardness scales involves empirical estimates, not exact equivalences. *

 HRC Ranges for Common Applications — Quick Reference

If you are selecting tool steel hardness based on the application & the grade, here is a practical quick-reference guide:

Application	Recommended HRC	Recommended Grade
Aluminium die inserts	44–48 HRC	H13 tool steel / DIN 1.2344 ESR
Aluminium extrusion dies	48–52 HRC	H13 tool steel / DIN 1.2344
Hot forging dies (heavy hammers)	40–45 HRC	H13 or H11
Hot forging dies (mechanical press)	46–50 HRC	H13
Cold stamping and blanking dies	58–62 HRC	D2 tool steel / DIN 1.2379
Cold forming and bending dies	56–60 HRC	D2 or A2
Plastic injection mould cavities	48–54 HRC	H13 or P20+Ni
Plastic injection mould bases	28–32 HRC	P20 / DIN 1.2311
Drill bits and taps	62–65 HRC	M2 / DIN 3343
Cutting and slitting knives	58–62 HRC	D2 or M2
Punches (light impact)	58–62 HRC	D2
Punches (heavy impact)	52–58 HRC	H13
Gauges and measuring tools	58–64 HRC	D2 or EN31

 What Happens if HRC is Too High or Too Low?

1. If HRC is too high
The die becomes too hard and brittle.

·         More chances of cracking or breaking under impact or stress

·         In hot work, heat checking (small surface cracks) starts earlier

·         Sharp corners and weak areas may fracture suddenly

·         Failure can happen without warning

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2. If HRC is too low
The die becomes too soft.

·         Surface wears out quickly

·         Shape and size accuracy reduce over time

·         Can deform permanently under heavy pressure

·         In die casting, molten metal may stick to the die (soldering)

·         In cutting/stamping, edges become dull or chip fast

·         Failure is gradual, but die life becomes much shorter

So, the correct HRC should balance hardness and toughness for the application.

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 What to check on the MTC

1. Verify the hardness is within the specification for the supply condition. H13 in annealed supply should not exceed 229 HBW. Higher values may indicate the material was not properly annealed.

 2. Check for uniformity. If multiple hardness readings are reported from different locations in the bar, they should be consistent. Large variation in hardness across a section is a warning sign of segregation or poor annealing.

 3. Confirm the test method. Brinell (HBW) and Vickers (HV) hardness values on the certificate are not directly comparable to HRC values you may see on a datasheet — use the conversion table above if comparison is needed.

 4. For pre-hardened grades (P20): Verify the HRC range corresponds to 28–32 HRC. Values outside this range may indicate the steel will machine differently than expected or may not meet the performance requirements of the mould design.

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 Frequently Asked Questions

 1. What HRC stands for in steel?

HRC stands for Hardness Rockwell C, a standard hardness scale for hardened tool steels. Higher HRC means harder and more wear-resistant steel.

2. What HRC is H13 tool steel?
H13 is typically hardened to 40–52 HRC depending on use:

·         Die casting: 44–48 HRC

·         Extrusion/plastic moulds: 48–52 HRC

·         Forging dies: 40–44 HRC

3. What is the HRC of D2 steel?
D2 is usually hardened to 55–62 HRC for stamping and blanking applications.

4. What is the difference between HRC and HB hardness?
HRC uses a diamond cone and measures depth; HB (Brinell) uses a ball indenter and measures impression size.

5. Is higher HRC always better for dies?
No. Higher HRC improves wear resistance but reduces toughness, increasing crack risk.

6. What HRC should I specify for a plastic injection mould?

·         P20: 28–32 HRC

·         H13: 48–52 HRC for longer runs or abrasive materials

7. Can I check tool steel hardness without a lab?
Yes. Use portable Rockwell or Leeb hardness testers for quick on-site checking.

8. What hardness should I specify when ordering H13?
H13 is usually supplied soft-annealed (max 229 HBW) for machining or can be supplied pre-hardened (30–36 HRC) / fully hardened as required.

9. Why do two steels with the same HRC perform differently?

 HRC alone doesn’t tell the full story & performance also depends on:

·        Chemical composition

·        Heat treatment quality

·        Grain structure

·        Alloying elements

10. What is the HRC of DB6 steel for forging dies?

For forging dies, DB6 is commonly used around 38–42 HRC to balance toughness and wear resistance. It is known for better toughness than H13 in heavy-impact applications.

·         Pre-hardened condition: 360–430 BHN (approx. 38–45 HRC)

·         Fully hardened / heat-treated: up to 50–55 HRC

·         Annealed condition: max 240–255 BHN

Conclusion

 At Virat Steels, we help customers across India choose the right tool steel grade, correct HRC, and suitable size/form for die casting, forging, extrusion, and plastic moulding applications backed by stock availability, test certificates, and ultrasonic-tested material.

 📞+91 98140-21775 |🌐 www.viratsteels.com |✉ info@viratsteels.com